Sandy is right about the counter... 10x the number of rolls of film run through the camera.
I have been using the GW670 II for about ten years, not sure of the number of rolls I have put through it though. I did have the focusing repaired on it... my younger daughter jumped on it when she was little and...
I really like using this camera. Several images in my personal gallery here at APUG are from this camera.
I picked up a used GSW690 III a couple of years ago. This is also a fine camera, love using it. The weight difference between the II and III is minimal, not enough to worry about.
The pricing you mention is fair. And like Sandy, I would not part with either of these two cameras for that amount.
Good luck.

gene